The invention relates in general to devices for steering projectiles and in particular to micro-electromechanical systems (MEMS) type control surfaces for steering projectiles.
Conventional control systems rely on actuators to rotate fins to provide flight path control. These fins protrude far into the flow stream and require actuators that provide sufficient torque to maintain the fins in the desired orientation. MEMS have been demonstrated for flight control on delta wings. Small perturbations in the flow field created by MEMS structures can result in a net macro force with sufficient strength to steer large objects.
U.S. Pat. No. 6,105,904 discloses deployable flow control devices. FIGS. 15 and 16 of that patent show two embodiments in which a sealable, flexible element acts as a flow effector. FIG. 15 shows the sealable, flexible element in the quiescent state while FIG. 15A shows it in the deformed state. The sealable, flexible element secures to the housing under lip. When plenum is not pressurized the sealable, flexible element is in its quiescent state, retracted out of the fluid boundary layer on the flow surface and within the housing. When the plenum is pressurized, the sealable, flexible element changes to its deformed state expanding such that it deploys through aperture into the fluid boundary layer on the flow surface. When the plenum is depressurized, the sealable, flexible element returns to its quiescent state and retracts out of the fluid boundary layer on the flow surface. FIGS. 16 and 16A show the sealable, flexible element attached to the flow surface rather than the housing.
One problem with the device disclosed in U.S. Pat. No. 6,105,904 is that the flow effector is a separate piece that must be attached in some manner to the projectile flow surface or skin. At high velocities, such as Mach 2 to Mach 10, the temperature of the projectile flow surface increases to several hundred degrees Centigrade, which causes weakness at areas where the flow effector is attached to the flow surface. Another problem is using a polymer as the material for the flow effector. At high velocities and temperatures, the polymer is too elastic and unstable. Still another problem is that, in the embodiment of FIG. 15, the flow effector is not flush with the flow surface, thereby creating a flow disturbance when the flow effector is in the “inactive” position. Similarly, in the embodiment of FIG. 16, the flow effector projects above the flow surface even in the “inactive” position.
Unexpectedly, Applicant has discovered a novel structural arrangement to overcome the above limitations.